A prophet during the Second Temple era.
A prophet. He has his own book in the Tanach, (Trei Asar/Twelve Prophets).
Chaggai, Zechariah, and Malachi all prophesied in the second year of [the reign of] Darius (Tractate Megillah 15a).
Chaggai, Zechariah, and Malachi received the traditions of the Torah from the prophets [before them] (Avot d'Rabbi Natan I).
Malachi is Mordechai. Why is he called Malachi? Because he was second to the king (melech) [and was looked upon as an angel (mal'ach) (Maharsha)]. However the Talmud in Tractate Megillah (p. 15a) concludes that Malachi is Ezra.
The Aramaic translation of the prophets was written by Yonatan ben Uziel, who had heard it [via his teachers (Maharsha, Tractate Megillah 3a)] from Chaggai, Zechariah, and Malachi (ibid.).
"I, Daniel, alone saw the vision; but the people who were with me did not see" (Daniel 10:7). This [refers to] Chaggai, Zechariah, and Malachi. They were superior to him in that they were prophets [who were sent by God to relate prophesies to Israel] whereas he was not [sent with a prophesy], and he was superior to them in that he saw [the vision] whereas they did not (Tractate Sanhedrin 93b; see Maharsha).
With the deaths of the last prophets - Chaggai, Zechariah, and Malachi - Divine Inspiration departed from Israel (Tractate Yoma 9b).
May the merit of the tzaddik Malachi HaNavie protect us all, Amen.